In recent years, a motor is generally used at a high-speed rotation for high power and high efficiency of the motor. However, when the motor is rotated at a high speed, an idling phenomenon (generally called as a creeping phenomenon) tends to occur where its ball bearings slidably rotate in the circumferential direction within bearing housings, in between the ball bearings that support a rotator and the bearing housings of brackets that hold the ball bearings. For this reason, to prevent such the creeping phenomenon, technologies have been conventionally known in which the bearing housings and bearing outer rings for the ball bearings are fitted and fixed by using an adhesive, or alternatively are prevented mechanically from idling by using an anti-idling stopper (Patent Literature 1, for example).
However, such the conventional configuration in which the bearing housings and the bearing outer rings for the ball bearings are fittingly fixed or fixed by using the adhesive has had the following drawbacks caused by heat generation during operation of the motor. That is, this results in the occurrence of a dimensional difference between a dimension between two ball bearing outer rings (generally called as a bearing outer-ring-to-outer-ring dimension) and a dimension between two ball bearing inner rings (generally called as a bearing inner-ring-to-inner-ring dimension), due to differences in thermal expansion coefficients. Then, when the bearing outer rings and the bearing housings are fixed using an adhesive or the like, the dimensional difference greatly influences the ball bearings to cause a backlash inside the ball bearings, leading to problems of, such as, the occurrence of abnormal vibrations and sounds and a breakage of the bearings. In particular, when synthetic-resin brackets are used, the dimensional difference is distinguished between a bearing housing-to-housing dimension and a ball bearing-to-bearing dimension.
Moreover, in Patent Literature 1, the configuration for preventing the idling is configured with a ring part fixed by press-fitting onto the outer ring of the ball bearing, a stopper included in a metal stopper member configured with a flange part, and a fitting part disposed in a resin frame member. Unfortunately, there has been a problem that the configuration disclosed in Patent Literature 1 requires the additional part, i.e. the stopper member, resulting in higher costs. In addition, according to the configuration disclosed in Patent Literature 1, the area becomes narrower at which a bearing mounting part of the resin frame can hold the outer ring of the bearing. For this reason, it becomes difficult to secure the accuracy of holding the bearing outer ring at the bearing mounting part. This has also been a problem.